1. Field of the Invention
The present invention relates to a movement disorder monitor, and a method of measuring the severity of a subject's movement disorder. More particularly, it preferably relates to a monitor and method for the continuous monitoring of a movement disorder. The present invention further, optionally, uses the monitor and method of the present invention to titrate or adjust a treatment delivery system including the delivery of drugs or electrical stimulation for treating or dosing a subject in response to changes in the severity of a subject's symptoms. The device and method disclosed herein further relate to monitoring symptoms of movement disorders, such as those associated with Parkinson's disease (PD), essential tremor, dystonia, and Tourette's syndrome, including tremor, bradykinesia, rigidity, gait/balance disturbances, and dyskinesia. Because essential tremor and PD are two of the most prevalent and life-altering types of movement disorders, essential tremor and PD will be the central examples used in describing the present invention. However, the device and method disclosed herein are equally adaptable for use in monitoring and assessing symptoms of any of the movement disorders mentioned herein or any other movement disorder that involves an inability to control movement of the body's extremities.
2. Technology Review
Parkinson's disease is characterized by unnatural motor movements. Most frequently these symptoms are manifested in the form of tremor, bradykinesia and/or rigidity of a subject's upper extremities. However, other symptoms associated with PD include negative effects on gait, balance, speech, olfaction, sleep and cognition. These symptoms are partly responsible for the subject's functional disability and social embarrassment. Various treatments have been developed to alleviate many of the symptoms of PD. The treatments can involve pharmaceutical interventions, fetal cell transplants, surgery, or electrical stimulation, such as deep brain stimulation (DBS) or functional electrical stimulation (FES), in some of these disorders. The efficacy of these interventions is often judged by the interventions' ability to alleviate patient symptoms and improve their quality of life. Furthermore, the efficacy of these interventions often varies greatly throughout the course of a single day, and throughout the course of treatment.
Tremors are one of the most common symptoms associated with movement disorders. They are involuntary muscle contractions characterized by oscillations of a body part. Tremor of the hands can be cosmetically upsetting and affect functional tasks such as grasping of objects. Resting tremors usually occur at frequencies of approximately 4-7 Hz while the frequency of action of postural tremors is higher, usually between 9-11 Hz. Tremor is a symptom often targeted by treatment. The standard clinical method for analyzing rest and postural or action tremor is qualitative assessment by a clinician and assignment of a score.
Bradykinesia refers to delays or hesitations in initiating movements and slowness in executing movements. The standard clinical method for analyzing bradykinesia is qualitative assessment by a clinician and assignment of a score. This score is assigned while the subject completes a repetitive finger-tapping task, a repetitive hand opening-closing task, and a pronation-supination task. Objective assessment by this means is difficult and variable. It has been found that movement rate and time are useful in better characterizing bradykinesia.
Rigidity occurs because muscles of the body are overly excited. The neurons involved in inhibition circuitry have died due to Parkinson's disease and muscles may receive continuous excitation. Rigidity causes the joints of the subject to become stiff and decreases range of motion. During normal movement, an agonist muscle contracts while the antagonist muscles relax. However, due to the constant motor unit input, the antagonist is unable to relax. Again, the standard clinical method for analyzing rigidity is qualitative assessment by a clinician and assignment of a score. To do so a clinician passively moves the subject's joints through a range of motion while the subject relaxes.
Dyskinesias are also one of the most common and disabling complications of chronic drug therapy. Dyskinesias are wild involuntary movements that typically occur when the benefit from the drug therapy is at its maximum. Clinical assessment of dyskinesias typically relies on self-reporting by the subject. There is a great need to objectively quantify these involuntary movements in view of the growing number of pharmacologic agents and surgical procedures to improve dyskinesia.
Gait and balance disturbances are also one of the more severe symptoms of movement disorders. In addition to the obvious effects on a subject's daily living such as mobility and independence, gait and balance disturbances may also lead to falls and additional physical and emotional trauma for suffering subjects. Such disturbances are also subject to a great deal of variance throughout the course of a single day, even while treated, making them difficult to control without a detailed understanding of each individual's disorder.
Standard clinical evaluation involves qualitative assessment of these symptoms. The current standard in evaluating the severity of movement disorder symptoms in Parkinson's disease is the Unified Parkinson's Disease Rating Scale (UPDRS) used to score motor tests, many of which involve repetitive movement tasks such as touching the nose and drawing the hand away repeatedly, or rapidly tapping the fingers together. A battery of exercises, typically a subset of the upper extremity motor section of the UPDRS, is normally completed during sessions to evaluate medication and DBS efficacy, while a clinician qualitatively assesses symptoms. Each test is evaluated by a clinician based solely on subjective visual observation and graded on a scale that ranges from 0 (normal) to 4 (severe). Like the UPDRS, the Tremor Research Group Essential Tremor Rating Assessment Scale (TETRAS), Washington Heights-Inwood Genetic Study of Essential Tremor (WHIGET) tremor rating scale, and Fahn-Tolosa-Marin tremor rating scale (TRS) are also used to evaluate essential tremor on a 0-4 scale.
In an effort to make these ratings more objective, recently some efforts have been made to quantify symptoms of movement disorders. Accelerometers and gyroscopes have been used individually to quantify some of these movement disorder symptoms, however, alone each sensor has limitations. Accelerometers operate in response to the local gravitational field; therefore they often have problems in separating changes in linear acceleration from rotation. Further, results of a second integration required to obtain linear position are often contaminated with noise, making measurement difficult at best. Gyroscopes measure angular velocity independent of gravity with a good frequency response; however, static angular position cannot be measured accurately due to DC drift characteristic with these devices. Combining the information from both accelerometers and gyroscopes can provide a more accurate method of quantifying motion.
Currently, many systems are tethered or bulky, which reduces patient safety, limits home monitoring capabilities, and does not allow for recording of some movement disorder symptoms. Additionally, none of the current systems have software to distinguish symptoms such as tremor and dyskinesia from activities of daily living (ADL), and relate them to standard rating scales such as the UPDRS or TRS. Finally, none of these systems have clinical video instruction or real-time clinical video feedback during continuous monitoring of movement disorders. In all of the treatment methods listed above, it is clear that improved outcomes and management of movement disorder symptoms could be achieved if a clinician were able to obtain objective data on a subject's symptoms beyond that which could be observed in the relatively short time period during which a subject sees a physician or other clinician during a standard office visit.
Accordingly, it is an object of the present invention to provide a device and method for accurately quantifying symptoms of movement disorders. It is still another object of the present invention to provide a system, which accurately quantifies symptoms utilizing both kinetic information and electromyography (EMG) data. It is further an object of the present invention to provide a wireless movement disorder system that can be worn continuously to provide continuous information to be analyzed as needed by the clinician. It is still further another object of the present invention to provide a movement disorder system that can provide analysis in real-time. It is still further another object of the present invention to provide a movement disorder system to allow for home monitoring of symptoms in subject's with these movement disorders to capture the complex fluctuation patterns of the disease over the course of days, weeks, months, or years. It is still further another object of the present invention to correlate a subject's symptoms with certain physiological, environmental and other factors, as well as the subject's assessment of his or her symptoms. It is still further another object of the present invention to distinguish between movement disorder symptoms and activities of daily living based at least in part on the quantitative recorded movement data. It is still further another object of the present invention to maximize subject safety. It is still further an object of the present invention to provide a system with clinical video instruction and real-time clinical video feedback. It is still further an object of the present invention to provide a treatment delivery system that can monitor symptoms in subject's and deliver treatment in response to those symptoms. Finally it is the object of the present invention to provide remote access between the clinician and subject.